1. Field of the Invention
The invention relates to multiple channel video systems, such as security systems and more particularly to such systems that perform video content analysis.
2. Background
In many instances, it is useful for video to be analyzed automatically by a computer system rather than having a person watch the video. For example, in a security system, a human observer is not likely to be sufficiently observant to catch a sudden change in a scene which remains changeless for hours at a time. Also, it is useful to have multiple scenes interpreted by a single observer. For example, one security guard may observe the goings on in multiple scenes captured by different cameras.
In domestic applications, video content from multiple sources, such as multiple channels, may be received and analyzed to automatically recommend changing a channel. For example, the printed name of a favorite actor might be found on one channel while the user is watching another channel.
The general field of video content analysis is a broad one involving many different motives for analyzing video content. But, generally speaking, “simple” surveillance devices such as video motion detectors and VCRs are designed and built to work with multiple channels of input. This decreases the amount of equipment a user has to buy and offers greatly increased value for money. However, more sophisticated video processing, such as that available as PC software, or as high-end motion detector modules, is designed to work on a single channel at a single time. For example, in advanced security systems, content analysis devices are designed to work on one channel at a time, requiring the users to purchase multiple devices, one for each “analyzed” channel.
Referring to FIG. 1, in a typical advanced security system, for example, video data is received from a video source 100 which may be, for example, data from a camera. A piece of ancillary equipment 195, such as a video recorder, may be somewhere in the data loop. A content analysis process 110 receives the data (perhaps in parallel or in series as indicated) analyzes it and presents results 120 to some other process, for example, an alarm process.
One system can be used to analyze multiple channels by scanning in a round robin fashion, but real time information may be lost by doing that, such as calculated data that rely on motion data. A principal cause of this delay is that fact that each analogue video signal needs to be digitized before it can be processed digitally. Switching from one signal to the next may incur a delay of up to one frame time while the digitizer attempts to synchronize with the sync of the new source. Thus for four video signals, the frame rate is not just four times less than for one signal; it may be as much as eight times less. Also, if an intervening piece of ancillary equipment, such as a video recorder, is in the loop, the rotating of multiple channels through that loop could make the data unusable for purposes of that ancillary equipment.
There exists a need in the art for ways of providing content analysis without the need for the purchase of multiple systems for providing content analysis and with provision for correct real time information.